The invention relates to a bonding system, and in particular, a bonding system for bonding wires between a semiconductor chip and a substrate on which the semiconductor chip is mounted.
During the packaging of semiconductor devices, it is common to mount a semiconductor chip (or die) on a substrate, such as a lead frame or a printed circuit board. A wire bonder is then used to form wire bonds between electrical input/output contact pads (or bond pads) on the die and electrical contact surfaces on the substrate. The wire bonder operates under control of a bonding program stored on the wire bonder that includes a set of bonding parameters, which are generally specific to each die/substrate combination. For example, the bonding parameters can include bond coordinates, bonding force, bonding time, ultrasonic power and electric flame off control for free air ball formation.
Due to variations between individual wire bonders and/or individual dies and substrates, it is usually necessary for an operator to modify the bonding parameters used on a specific wire bonder to ensure that satisfactory bonds are formed between the correct corresponding bond pads and contact surfaces on the substrate.
However, this also creates problems as an operator may inadvertently modify the bonding parameters so that erroneous bonds are performed by the wire bonder.
In accordance with a first aspect of the present invention, there is provided a bonding system for bonding wires between a first electrical contact surface on a semiconductor chip and a second electrical contact surface on a substrate, the bonding system comprising a first memory device having a master bond program stored thereon, a second memory device having an operating bond program stored thereon, the operating bond program being generated by transferring a copy of the master bond program from the first memory device to the second memory device, the second memory device being adapted to permit a parameter of the operating bond program to be modified; a processing device coupled to the first and second memory devices; an input device coupled to the processing device; and an output device coupled to the processing device; the processing device, on receiving an input signal from the input device to modify a parameter of the operating bond program, comparing the modified parameter with the corresponding parameter in the master bond program and storing the modified parameter in the operating bond program if the modified parameter is within a tolerance of the corresponding parameter in the master bond program, and the processing device outputting a signal to the output device if the modified parameter is not within the tolerance.
An advantage of the invention is that it enables an operator to modify bond parameters while verifying the modified parameters with the master bond program to minimise the risk of an operator inadvertently modifying a parameter so that the wire bonder performs an incorrect or unreliable bond.
Preferably, the parameters which may be modified comprise bonding coordinates for the first and/or second contact surface.
Typically, the bond parameters of the operating program which may be modified comprise bond process parameters, such as bonding force, ultrasonic bonding power, bonding times and electric flame off control for free air ball formation.
Preferably, if the modified perimeter is not within the tolerance of the corresponding parameter in the master bond program, the processor controls the wire bonder to stop wire bonding operations.
Typically, the tolerance for the bond parameter is predetermined and is preferably, stored in the master bond program.